Examples of devices which digitally recording and reproducing images and/or sound are the digital video cameras and the portable DVD players. These devices use a digital video cassette (DV tape cassette), a digital video disk (DVD) or the like as a recording medium. However, since these devices require a high bit rate, a duration for which recording can be performed (“recording time”) or a duration for which reproduction can be performed (“reproduction time”) is shorter although these devices have a large size.
Various portable terminal type digital recording/reproduction apparatuses that overcome the above mentioned problem by using an efficient memory than the conventional recording media have been suggested. These apparatuses receive and code a video input and a sound input and record them into the memory card such as a multimedia card (MMC) that utilizes a flash memory, a Smart Media (Trademark) , or a SD (Secure Density) card as a recording medium, and decode the recorded data and reproduce them. Moreover, recently a portable terminal type digital recording/reproduction apparatus using a very small sized and low-capacity magneto-optical disk as a recording medium have also been suggested. This magneto-optical disk has a capacity of between 500 MB and 2 GB, and a size between 2 inches to less than or equal to 3 cm. In this magneto-optical disk, recording can be carried out with a lower bit rate than the above-mentioned conventional recording media, and as a result the recording time can be made longer.
However, in the conventional portable digital recording/reproduction apparatus, when a dynamic image or sound is coded, mostly a frame rate or a bit rate is always constant regardless of a type of dynamic image contents and image size. Therefore, the conventional portable digital recording/reproduction apparatus has problems, depending on the type of the dynamic image content (for example, news, drama), such that the quality of the reproduction is unsatisfactory, the dynamic image does not move sufficiently due to a low frame rate, and the recording time becomes short because the bit rate is made unnecessarily high. Problems similar to those mentioned above arise when the frame rate or the bit rate are not adjusted suitably according to differences in a screen size (in inch) and an image resolution (i.e. size of the dynamic image).